diff --git a/src/json.hpp b/src/json.hpp
index ff409559b..aed03fa37 100644
--- a/src/json.hpp
+++ b/src/json.hpp
@@ -261,10 +261,12 @@ class basic_json
     /// the type of an element const pointer
     using const_pointer = typename std::allocator_traits<allocator_type>::const_pointer;
 
+    // forward declaration for iterators
+    template <typename U> class iter_impl;
     /// an iterator for a basic_json container
-    class iterator;
+    using iterator = iter_impl<basic_json>;
     /// a const iterator for a basic_json container
-    class const_iterator;
+    using const_iterator = iter_impl<const basic_json>;
     /// a reverse iterator for a basic_json container
     using reverse_iterator = json_reverse_iterator<typename basic_json::iterator>;
     /// a const reverse iterator for a basic_json container
@@ -8204,10 +8206,10 @@ class basic_json
 
   public:
     /*!
-    @brief a const random access iterator for the @ref basic_json class
+    @brief a template for a random access iterator for the @ref basic_json class
 
-    This class implements a const iterator for the @ref basic_json class. From
-    this class, the @ref iterator class is derived.
+    This class implements a both iterators (iterator and const_iterator) 
+    for the @ref basic_json class.
 
     @note An iterator is called *initialized* when a pointer to a JSON value
           has been set (e.g., by a constructor or a copy assignment). If the
@@ -8222,25 +8224,35 @@ class basic_json
 
     @since version 1.0.0
     */
-    class const_iterator : public std::iterator<std::random_access_iterator_tag, const basic_json>
+    template <typename U>
+    class iter_impl : public std::iterator<std::random_access_iterator_tag, U>
     {
         /// allow basic_json to access private members
         friend class basic_json;
 
+        // make sure U is basic_json or const basic_json
+        static_assert(std::is_same<U, basic_json>::value
+                      or std::is_same<U, const basic_json>::value,
+                      "iter_impl only accepts (const) basic_json");
+
       public:
         /// the type of the values when the iterator is dereferenced
         using value_type = typename basic_json::value_type;
         /// a type to represent differences between iterators
         using difference_type = typename basic_json::difference_type;
         /// defines a pointer to the type iterated over (value_type)
-        using pointer = typename basic_json::const_pointer;
+        using pointer = typename std::conditional<std::is_const<U>::value,
+                                                  typename basic_json::const_pointer,
+                                                  typename basic_json::pointer>::type;
         /// defines a reference to the type iterated over (value_type)
-        using reference = typename basic_json::const_reference;
+        using reference = typename std::conditional<std::is_const<U>::value,
+                                                    typename basic_json::const_reference,
+                                                    typename basic_json::reference>::type;
         /// the category of the iterator
         using iterator_category = std::bidirectional_iterator_tag;
 
         /// default constructor
-        const_iterator() = default;
+        iter_impl() = default;
 
         /*!
         @brief constructor for a given JSON instance
@@ -8248,7 +8260,7 @@ class basic_json
         @pre object != nullptr
         @post The iterator is initialized; i.e. `m_object != nullptr`.
         */
-        explicit const_iterator(pointer object) noexcept
+        explicit iter_impl(pointer object) noexcept
             : m_object(object)
         {
             assert(m_object != nullptr);
@@ -8275,37 +8287,25 @@ class basic_json
             }
         }
 
-        /*!
-        @brief copy constructor given a non-const iterator
-        @param[in] other  iterator to copy from
-        @note It is not checked whether @a other is initialized.
+        /*
+        Use operator const_iterator instead of 
+        const_iterator(const iterator& other) noexcept
+        to avoid two class definitions for iterator and const_iterator.
+
+        This function is only called if this class is an iterator.
+        If this class is a const_iterator this function is not called.
         */
-        explicit const_iterator(const iterator& other) noexcept
-            : m_object(other.m_object)
-        {
-            if (m_object != nullptr)
-            {
-                switch (m_object->m_type)
-                {
-                    case basic_json::value_t::object:
-                    {
-                        m_it.object_iterator = other.m_it.object_iterator;
-                        break;
-                    }
+        operator const_iterator() const
+         {
+             const_iterator ret;
 
-                    case basic_json::value_t::array:
-                    {
-                        m_it.array_iterator = other.m_it.array_iterator;
-                        break;
-                    }
-
-                    default:
-                    {
-                        m_it.primitive_iterator = other.m_it.primitive_iterator;
-                        break;
-                    }
-                }
+            if (m_object)
+             {
+                ret.m_object = m_object;
+                ret.m_it = m_it;
             }
+
+            return ret;
         }
 
         /*!
@@ -8313,7 +8313,7 @@ class basic_json
         @param[in] other  iterator to copy from
         @note It is not checked whether @a other is initialized.
         */
-        const_iterator(const const_iterator& other) noexcept
+        iter_impl(const iter_impl& other) noexcept
             : m_object(other.m_object), m_it(other.m_it)
         {}
 
@@ -8322,7 +8322,7 @@ class basic_json
         @param[in,out] other  iterator to copy from
         @note It is not checked whether @a other is initialized.
         */
-        const_iterator& operator=(const_iterator other) noexcept(
+        iter_impl& operator=(iter_impl other) noexcept(
             std::is_nothrow_move_constructible<pointer>::value and
             std::is_nothrow_move_assignable<pointer>::value and
             std::is_nothrow_move_constructible<internal_iterator>::value and
@@ -8484,7 +8484,7 @@ class basic_json
         @brief post-increment (it++)
         @pre The iterator is initialized; i.e. `m_object != nullptr`.
         */
-        const_iterator operator++(int)
+        iter_impl operator++(int)
         {
             auto result = *this;
             ++(*this);
@@ -8495,7 +8495,7 @@ class basic_json
         @brief pre-increment (++it)
         @pre The iterator is initialized; i.e. `m_object != nullptr`.
         */
-        const_iterator& operator++()
+        iter_impl& operator++()
         {
             assert(m_object != nullptr);
 
@@ -8527,7 +8527,7 @@ class basic_json
         @brief post-decrement (it--)
         @pre The iterator is initialized; i.e. `m_object != nullptr`.
         */
-        const_iterator operator--(int)
+        iter_impl operator--(int)
         {
             auto result = *this;
             --(*this);
@@ -8538,7 +8538,7 @@ class basic_json
         @brief pre-decrement (--it)
         @pre The iterator is initialized; i.e. `m_object != nullptr`.
         */
-        const_iterator& operator--()
+        iter_impl& operator--()
         {
             assert(m_object != nullptr);
 
@@ -8570,7 +8570,7 @@ class basic_json
         @brief  comparison: equal
         @pre The iterator is initialized; i.e. `m_object != nullptr`.
         */
-        bool operator==(const const_iterator& other) const
+        bool operator==(const iter_impl& other) const
         {
             // if objects are not the same, the comparison is undefined
             if (m_object != other.m_object)
@@ -8603,7 +8603,7 @@ class basic_json
         @brief  comparison: not equal
         @pre The iterator is initialized; i.e. `m_object != nullptr`.
         */
-        bool operator!=(const const_iterator& other) const
+        bool operator!=(const iter_impl& other) const
         {
             return not operator==(other);
         }
@@ -8612,7 +8612,7 @@ class basic_json
         @brief  comparison: smaller
         @pre The iterator is initialized; i.e. `m_object != nullptr`.
         */
-        bool operator<(const const_iterator& other) const
+        bool operator<(const iter_impl& other) const
         {
             // if objects are not the same, the comparison is undefined
             if (m_object != other.m_object)
@@ -8645,7 +8645,7 @@ class basic_json
         @brief  comparison: less than or equal
         @pre The iterator is initialized; i.e. `m_object != nullptr`.
         */
-        bool operator<=(const const_iterator& other) const
+        bool operator<=(const iter_impl& other) const
         {
             return not other.operator < (*this);
         }
@@ -8654,7 +8654,7 @@ class basic_json
         @brief  comparison: greater than
         @pre The iterator is initialized; i.e. `m_object != nullptr`.
         */
-        bool operator>(const const_iterator& other) const
+        bool operator>(const iter_impl& other) const
         {
             return not operator<=(other);
         }
@@ -8663,7 +8663,7 @@ class basic_json
         @brief  comparison: greater than or equal
         @pre The iterator is initialized; i.e. `m_object != nullptr`.
         */
-        bool operator>=(const const_iterator& other) const
+        bool operator>=(const iter_impl& other) const
         {
             return not operator<(other);
         }
@@ -8672,7 +8672,7 @@ class basic_json
         @brief  add to iterator
         @pre The iterator is initialized; i.e. `m_object != nullptr`.
         */
-        const_iterator& operator+=(difference_type i)
+        iter_impl& operator+=(difference_type i)
         {
             assert(m_object != nullptr);
 
@@ -8703,7 +8703,7 @@ class basic_json
         @brief  subtract from iterator
         @pre The iterator is initialized; i.e. `m_object != nullptr`.
         */
-        const_iterator& operator-=(difference_type i)
+        iter_impl& operator-=(difference_type i)
         {
             return operator+=(-i);
         }
@@ -8712,7 +8712,7 @@ class basic_json
         @brief  add to iterator
         @pre The iterator is initialized; i.e. `m_object != nullptr`.
         */
-        const_iterator operator+(difference_type i)
+        iter_impl operator+(difference_type i)
         {
             auto result = *this;
             result += i;
@@ -8723,7 +8723,7 @@ class basic_json
         @brief  subtract from iterator
         @pre The iterator is initialized; i.e. `m_object != nullptr`.
         */
-        const_iterator operator-(difference_type i)
+        iter_impl operator-(difference_type i)
         {
             auto result = *this;
             result -= i;
@@ -8734,7 +8734,7 @@ class basic_json
         @brief  return difference
         @pre The iterator is initialized; i.e. `m_object != nullptr`.
         */
-        difference_type operator-(const const_iterator& other) const
+        difference_type operator-(const iter_impl& other) const
         {
             assert(m_object != nullptr);
 
@@ -8830,141 +8830,6 @@ class basic_json
         internal_iterator m_it = internal_iterator();
     };
 
-    /*!
-    @brief a mutable random access iterator for the @ref basic_json class
-
-    @requirement The class satisfies the following concept requirements:
-    - [RandomAccessIterator](http://en.cppreference.com/w/cpp/concept/RandomAccessIterator):
-      The iterator that can be moved to point (forward and backward) to any
-      element in constant time.
-    - [OutputIterator](http://en.cppreference.com/w/cpp/concept/OutputIterator):
-      It is possible to write to the pointed-to element.
-
-    @since version 1.0.0
-    */
-    class iterator : public const_iterator
-    {
-      public:
-        using base_iterator = const_iterator;
-        using pointer = typename basic_json::pointer;
-        using reference = typename basic_json::reference;
-
-        /// default constructor
-        iterator() = default;
-
-        /// constructor for a given JSON instance
-        explicit iterator(pointer object) noexcept
-            : base_iterator(object)
-        {}
-
-        /// copy constructor
-        iterator(const iterator& other) noexcept
-            : base_iterator(other)
-        {}
-
-        /// copy assignment
-        iterator& operator=(iterator other) noexcept(
-            std::is_nothrow_move_constructible<pointer>::value and
-            std::is_nothrow_move_assignable<pointer>::value and
-            std::is_nothrow_move_constructible<internal_iterator>::value and
-            std::is_nothrow_move_assignable<internal_iterator>::value
-        )
-        {
-            base_iterator::operator=(other);
-            return *this;
-        }
-
-        /// return a reference to the value pointed to by the iterator
-        reference operator*() const
-        {
-            return const_cast<reference>(base_iterator::operator*());
-        }
-
-        /// dereference the iterator
-        pointer operator->() const
-        {
-            return const_cast<pointer>(base_iterator::operator->());
-        }
-
-        /// post-increment (it++)
-        iterator operator++(int)
-        {
-            iterator result = *this;
-            base_iterator::operator++();
-            return result;
-        }
-
-        /// pre-increment (++it)
-        iterator& operator++()
-        {
-            base_iterator::operator++();
-            return *this;
-        }
-
-        /// post-decrement (it--)
-        iterator operator--(int)
-        {
-            iterator result = *this;
-            base_iterator::operator--();
-            return result;
-        }
-
-        /// pre-decrement (--it)
-        iterator& operator--()
-        {
-            base_iterator::operator--();
-            return *this;
-        }
-
-        /// add to iterator
-        iterator& operator+=(difference_type i)
-        {
-            base_iterator::operator+=(i);
-            return *this;
-        }
-
-        /// subtract from iterator
-        iterator& operator-=(difference_type i)
-        {
-            base_iterator::operator-=(i);
-            return *this;
-        }
-
-        /// add to iterator
-        iterator operator+(difference_type i)
-        {
-            auto result = *this;
-            result += i;
-            return result;
-        }
-
-        /// subtract from iterator
-        iterator operator-(difference_type i)
-        {
-            auto result = *this;
-            result -= i;
-            return result;
-        }
-
-        /// return difference
-        difference_type operator-(const iterator& other) const
-        {
-            return base_iterator::operator-(other);
-        }
-
-        /// access to successor
-        reference operator[](difference_type n) const
-        {
-            return const_cast<reference>(base_iterator::operator[](n));
-        }
-
-        /// return the value of an iterator
-        reference value() const
-        {
-            return const_cast<reference>(base_iterator::value());
-        }
-    };
-
     /*!
     @brief a template for a reverse iterator class
 
diff --git a/src/json.hpp.re2c b/src/json.hpp.re2c
index 4366fe6dc..17813c798 100644
--- a/src/json.hpp.re2c
+++ b/src/json.hpp.re2c
@@ -8204,10 +8204,10 @@ class basic_json
 
   public:
     /*!
-    @brief a const random access iterator for the @ref basic_json class
+    @brief a template for a random access iterator for the @ref basic_json class
 
-    This class implements a const iterator for the @ref basic_json class. From
-    this class, the @ref iterator class is derived.
+    This class implements a both iterators (iterator and const_iterator) 
+    for the @ref basic_json class.
 
     @note An iterator is called *initialized* when a pointer to a JSON value
           has been set (e.g., by a constructor or a copy assignment). If the
@@ -8222,25 +8222,35 @@ class basic_json
 
     @since version 1.0.0
     */
-    class const_iterator : public std::iterator<std::random_access_iterator_tag, const basic_json>
+    template <typename U>
+    class iter_impl : public std::iterator<std::random_access_iterator_tag, U>
     {
         /// allow basic_json to access private members
         friend class basic_json;
 
+        // make sure U is basic_json or const basic_json
+        static_assert(std::is_same<U, basic_json>::value
+                      or std::is_same<U, const basic_json>::value,
+                      "iter_impl only accepts (const) basic_json");
+
       public:
         /// the type of the values when the iterator is dereferenced
         using value_type = typename basic_json::value_type;
         /// a type to represent differences between iterators
         using difference_type = typename basic_json::difference_type;
         /// defines a pointer to the type iterated over (value_type)
-        using pointer = typename basic_json::const_pointer;
+        using pointer = typename std::conditional<std::is_const<U>::value,
+                                                  typename basic_json::const_pointer,
+                                                  typename basic_json::pointer>::type;
         /// defines a reference to the type iterated over (value_type)
-        using reference = typename basic_json::const_reference;
+        using reference = typename std::conditional<std::is_const<U>::value,
+                                                    typename basic_json::const_reference,
+                                                    typename basic_json::reference>::type;
         /// the category of the iterator
         using iterator_category = std::bidirectional_iterator_tag;
 
         /// default constructor
-        const_iterator() = default;
+        iter_impl() = default;
 
         /*!
         @brief constructor for a given JSON instance
@@ -8248,7 +8258,7 @@ class basic_json
         @pre object != nullptr
         @post The iterator is initialized; i.e. `m_object != nullptr`.
         */
-        explicit const_iterator(pointer object) noexcept
+        explicit iter_impl(pointer object) noexcept
             : m_object(object)
         {
             assert(m_object != nullptr);
@@ -8275,37 +8285,25 @@ class basic_json
             }
         }
 
-        /*!
-        @brief copy constructor given a non-const iterator
-        @param[in] other  iterator to copy from
-        @note It is not checked whether @a other is initialized.
+        /*
+        Use operator const_iterator instead of 
+        const_iterator(const iterator& other) noexcept
+        to avoid two class definitions for iterator and const_iterator.
+
+        This function is only called if this class is an iterator.
+        If this class is a const_iterator this function is not called.
         */
-        explicit const_iterator(const iterator& other) noexcept
-            : m_object(other.m_object)
-        {
-            if (m_object != nullptr)
-            {
-                switch (m_object->m_type)
-                {
-                    case basic_json::value_t::object:
-                    {
-                        m_it.object_iterator = other.m_it.object_iterator;
-                        break;
-                    }
+        operator const_iterator() const
+         {
+             const_iterator ret;
 
-                    case basic_json::value_t::array:
-                    {
-                        m_it.array_iterator = other.m_it.array_iterator;
-                        break;
-                    }
-
-                    default:
-                    {
-                        m_it.primitive_iterator = other.m_it.primitive_iterator;
-                        break;
-                    }
-                }
+            if (m_object)
+             {
+                ret.m_object = m_object;
+                ret.m_it = m_it;
             }
+
+            return ret;
         }
 
         /*!
@@ -8313,7 +8311,7 @@ class basic_json
         @param[in] other  iterator to copy from
         @note It is not checked whether @a other is initialized.
         */
-        const_iterator(const const_iterator& other) noexcept
+        iter_impl(const iter_impl& other) noexcept
             : m_object(other.m_object), m_it(other.m_it)
         {}
 
@@ -8322,7 +8320,7 @@ class basic_json
         @param[in,out] other  iterator to copy from
         @note It is not checked whether @a other is initialized.
         */
-        const_iterator& operator=(const_iterator other) noexcept(
+        iter_impl& operator=(iter_impl other) noexcept(
             std::is_nothrow_move_constructible<pointer>::value and
             std::is_nothrow_move_assignable<pointer>::value and
             std::is_nothrow_move_constructible<internal_iterator>::value and
@@ -8484,7 +8482,7 @@ class basic_json
         @brief post-increment (it++)
         @pre The iterator is initialized; i.e. `m_object != nullptr`.
         */
-        const_iterator operator++(int)
+        iter_impl operator++(int)
         {
             auto result = *this;
             ++(*this);
@@ -8495,7 +8493,7 @@ class basic_json
         @brief pre-increment (++it)
         @pre The iterator is initialized; i.e. `m_object != nullptr`.
         */
-        const_iterator& operator++()
+        iter_impl& operator++()
         {
             assert(m_object != nullptr);
 
@@ -8527,7 +8525,7 @@ class basic_json
         @brief post-decrement (it--)
         @pre The iterator is initialized; i.e. `m_object != nullptr`.
         */
-        const_iterator operator--(int)
+        iter_impl operator--(int)
         {
             auto result = *this;
             --(*this);
@@ -8538,7 +8536,7 @@ class basic_json
         @brief pre-decrement (--it)
         @pre The iterator is initialized; i.e. `m_object != nullptr`.
         */
-        const_iterator& operator--()
+        iter_impl& operator--()
         {
             assert(m_object != nullptr);
 
@@ -8570,7 +8568,7 @@ class basic_json
         @brief  comparison: equal
         @pre The iterator is initialized; i.e. `m_object != nullptr`.
         */
-        bool operator==(const const_iterator& other) const
+        bool operator==(const iter_impl& other) const
         {
             // if objects are not the same, the comparison is undefined
             if (m_object != other.m_object)
@@ -8603,7 +8601,7 @@ class basic_json
         @brief  comparison: not equal
         @pre The iterator is initialized; i.e. `m_object != nullptr`.
         */
-        bool operator!=(const const_iterator& other) const
+        bool operator!=(const iter_impl& other) const
         {
             return not operator==(other);
         }
@@ -8612,7 +8610,7 @@ class basic_json
         @brief  comparison: smaller
         @pre The iterator is initialized; i.e. `m_object != nullptr`.
         */
-        bool operator<(const const_iterator& other) const
+        bool operator<(const iter_impl& other) const
         {
             // if objects are not the same, the comparison is undefined
             if (m_object != other.m_object)
@@ -8645,7 +8643,7 @@ class basic_json
         @brief  comparison: less than or equal
         @pre The iterator is initialized; i.e. `m_object != nullptr`.
         */
-        bool operator<=(const const_iterator& other) const
+        bool operator<=(const iter_impl& other) const
         {
             return not other.operator < (*this);
         }
@@ -8654,7 +8652,7 @@ class basic_json
         @brief  comparison: greater than
         @pre The iterator is initialized; i.e. `m_object != nullptr`.
         */
-        bool operator>(const const_iterator& other) const
+        bool operator>(const iter_impl& other) const
         {
             return not operator<=(other);
         }
@@ -8663,7 +8661,7 @@ class basic_json
         @brief  comparison: greater than or equal
         @pre The iterator is initialized; i.e. `m_object != nullptr`.
         */
-        bool operator>=(const const_iterator& other) const
+        bool operator>=(const iter_impl& other) const
         {
             return not operator<(other);
         }
@@ -8672,7 +8670,7 @@ class basic_json
         @brief  add to iterator
         @pre The iterator is initialized; i.e. `m_object != nullptr`.
         */
-        const_iterator& operator+=(difference_type i)
+        iter_impl& operator+=(difference_type i)
         {
             assert(m_object != nullptr);
 
@@ -8703,7 +8701,7 @@ class basic_json
         @brief  subtract from iterator
         @pre The iterator is initialized; i.e. `m_object != nullptr`.
         */
-        const_iterator& operator-=(difference_type i)
+        iter_impl& operator-=(difference_type i)
         {
             return operator+=(-i);
         }
@@ -8712,7 +8710,7 @@ class basic_json
         @brief  add to iterator
         @pre The iterator is initialized; i.e. `m_object != nullptr`.
         */
-        const_iterator operator+(difference_type i)
+        iter_impl operator+(difference_type i)
         {
             auto result = *this;
             result += i;
@@ -8723,7 +8721,7 @@ class basic_json
         @brief  subtract from iterator
         @pre The iterator is initialized; i.e. `m_object != nullptr`.
         */
-        const_iterator operator-(difference_type i)
+        iter_impl operator-(difference_type i)
         {
             auto result = *this;
             result -= i;
@@ -8734,7 +8732,7 @@ class basic_json
         @brief  return difference
         @pre The iterator is initialized; i.e. `m_object != nullptr`.
         */
-        difference_type operator-(const const_iterator& other) const
+        difference_type operator-(const iter_impl& other) const
         {
             assert(m_object != nullptr);
 
@@ -8830,141 +8828,6 @@ class basic_json
         internal_iterator m_it = internal_iterator();
     };
 
-    /*!
-    @brief a mutable random access iterator for the @ref basic_json class
-
-    @requirement The class satisfies the following concept requirements:
-    - [RandomAccessIterator](http://en.cppreference.com/w/cpp/concept/RandomAccessIterator):
-      The iterator that can be moved to point (forward and backward) to any
-      element in constant time.
-    - [OutputIterator](http://en.cppreference.com/w/cpp/concept/OutputIterator):
-      It is possible to write to the pointed-to element.
-
-    @since version 1.0.0
-    */
-    class iterator : public const_iterator
-    {
-      public:
-        using base_iterator = const_iterator;
-        using pointer = typename basic_json::pointer;
-        using reference = typename basic_json::reference;
-
-        /// default constructor
-        iterator() = default;
-
-        /// constructor for a given JSON instance
-        explicit iterator(pointer object) noexcept
-            : base_iterator(object)
-        {}
-
-        /// copy constructor
-        iterator(const iterator& other) noexcept
-            : base_iterator(other)
-        {}
-
-        /// copy assignment
-        iterator& operator=(iterator other) noexcept(
-            std::is_nothrow_move_constructible<pointer>::value and
-            std::is_nothrow_move_assignable<pointer>::value and
-            std::is_nothrow_move_constructible<internal_iterator>::value and
-            std::is_nothrow_move_assignable<internal_iterator>::value
-        )
-        {
-            base_iterator::operator=(other);
-            return *this;
-        }
-
-        /// return a reference to the value pointed to by the iterator
-        reference operator*() const
-        {
-            return const_cast<reference>(base_iterator::operator*());
-        }
-
-        /// dereference the iterator
-        pointer operator->() const
-        {
-            return const_cast<pointer>(base_iterator::operator->());
-        }
-
-        /// post-increment (it++)
-        iterator operator++(int)
-        {
-            iterator result = *this;
-            base_iterator::operator++();
-            return result;
-        }
-
-        /// pre-increment (++it)
-        iterator& operator++()
-        {
-            base_iterator::operator++();
-            return *this;
-        }
-
-        /// post-decrement (it--)
-        iterator operator--(int)
-        {
-            iterator result = *this;
-            base_iterator::operator--();
-            return result;
-        }
-
-        /// pre-decrement (--it)
-        iterator& operator--()
-        {
-            base_iterator::operator--();
-            return *this;
-        }
-
-        /// add to iterator
-        iterator& operator+=(difference_type i)
-        {
-            base_iterator::operator+=(i);
-            return *this;
-        }
-
-        /// subtract from iterator
-        iterator& operator-=(difference_type i)
-        {
-            base_iterator::operator-=(i);
-            return *this;
-        }
-
-        /// add to iterator
-        iterator operator+(difference_type i)
-        {
-            auto result = *this;
-            result += i;
-            return result;
-        }
-
-        /// subtract from iterator
-        iterator operator-(difference_type i)
-        {
-            auto result = *this;
-            result -= i;
-            return result;
-        }
-
-        /// return difference
-        difference_type operator-(const iterator& other) const
-        {
-            return base_iterator::operator-(other);
-        }
-
-        /// access to successor
-        reference operator[](difference_type n) const
-        {
-            return const_cast<reference>(base_iterator::operator[](n));
-        }
-
-        /// return the value of an iterator
-        reference value() const
-        {
-            return const_cast<reference>(base_iterator::value());
-        }
-    };
-
     /*!
     @brief a template for a reverse iterator class